Goals. The candidate's basic goal is to understand the function of the descending, or efferent neural pathways in the auditory system. The immediate goal is to characterize the interaction between ascending and descending auditory systems at the level of the superior olivary complex. Research Project. To further these objectives, a robust in vitro preparation of the auditory brainstem has been developed using a mammal with unusual metabolic tolerances, the brown bat, Eptesicus fuscus. This slice preparation opens a difficult brainstem area to detailed study, allowing axons and cells to be intracellularly labeled in previously unattainable number and clarity. The initial project focus is the medical nucleus of the trapezoid body (MNTB), a superior olivary nucleus implicated in the circuitry of both ascending and descending systems. Intracellular labeling suggests that both the cells of the MNTB and the large ascending axons which contact these cells send collateral projections to several common targets. One important target is the periolivary cell group which forms the olivocochlear bundle, the principle descending auditory tract of the brainstem. The slice preparation is well suited to characterize this pivotal juncture between ascending and descending auditory systems. Effect of RCDA. This award will permit a sustained and concentrated effort toward the project goals. The award will also greatly enhance the candidate's opportunities to refine the brainstem tissue slice preparation and to develop the range of technical skills necessary to achieve these goals. Institution's Plans. Ohio University has pledged strong support of the candidate's research career development, in such forms as a vital research environment, continued encouragement of intra- and extramural collaborative interactions, and extensive research staff support and facilities.